1. Field of the Invention
The present invention relates to a pavement structure examination vehicle which examines a structure of the ground of a paved road while traveling at high velocity on the paved road.
2. Description of the Related Art
The ground structure of a paved road is composed of a roadbed A and a paved floor B on the roadbed A as shown in FIG. 11, and the roadbed A comprises, for example, a sand layer 2 rammed down on a miscellaneous soil layer 1 which is mixed with ballasts and crushed matters, and the paved floor B is composed of, for example, three asphalt layers 3, 4 and 5 in which the size of a mixed gravel is decreased in order from the gravel included in the bottom asphalt layer 3 which is located on the sand layer 2 to the gravel in the uppermost layer 5 which forms the road surface.
As a method for examining the structure of a ground of the paved road, a method using an underground radar means based on the electromagnetic wave reflection method has been known in the art.
The principle of this method is that pulsed electromagnetic waves radiated from an antenna reflect partially at respective borders of layers which have electrically different properties (dielectric constant) as shown in FIG. 5. When the ground structure of a paved road is composed of a plurality of layers, reflection waves are generated in the same number as that of the layers and a series of pulses are observed in a time-delayed manner.
The time difference between pulses corresponds to the time required by the passage of the pulse through the layer.
An electromagnetic wave has a different velocity according to the difference of the dielectric constant of a medium. Generally the velocity of an electromagnetic wave in natural substances is much less than that of 300 thousand km per second in vacuum. Therefore, when the time is converted into the distance by using the velocity of the electromagnetic wave in these substances, the actual state of the layer of the ground can be made clear.
When a measuring apparatus (such as underground radar) is moved continuously radiating pulses of electromagnetic waves, the reflection of the pulses are received on a sheet as a plane belt-form record with changing patterns, and further, when the intensity of reflection of pulses are put out in light and shade expression, the records such as shown in FIG. 6 can be printed out.
Then the examination for discovering the ground of a defective structure is conducted on the basis of this data, and the structure of the ground is actually investigated by such as digging of the paved road of the place thus discovered.
The examination of the paved road in this way is now conducted manually by running a vehicle mounted with a radar at low speed, so that this examination has been often conducted at night when the traffic is light, thereby minimizing problems of a risk of accident.
Also there has been a problem that the position of the road can not be detected correctly and easily from the data shown in FIG. 6, and it takes time to determine the position to be investigated.
Further, though the instruments to be used in the actual examination of the ground can be miniaturized according to the examination method developed by the applicant, they are all mounted on a vehicle other than the vehicle mounted with the aforementioned radar, so that it has been desired that all the equipment and instruments are mounted in one vehicle.